When men are walking with the woman they love, they slow down their pace.

In general, men tend to walk faster than women (I know ladies, I’m skeptical too). But it’s true. That’s because walking speed is determined by physical features and using them in a way that minimizes energy expenditure. Mass and lower limb length influence walking speed, and in general, men tend to be higher in both.

What scientists say is unclear is what happens when a man and a woman walk together. If someone has to change their speed to align with the other, who will do it? It turns out, it’s consistently the men.

To study this, the researchers from Seattle Pacific University in Washington studied the walking speed choices of eleven men and eleven women as they walked around a track alone, with friends of the same and opposite sex, and with a significant other holding hands or hands-free.

In their study, released Wednesday, they found that when walking with women, men significantly slow their pace to their companions’, but only if the woman is their romantic partner. Walking with friends, whether it be friends of the same or opposite sex, did not significantly change pace for anyone, and women only slightly changed their pace when walking with their partner. The authors say this suggests that adjusting stride only happens for romantic partners.

Biologically speaking, the researchers say it makes sense that men are more likely to take on an energetic burden to accommodate their lover. That’s because a woman’s reproductive system is sensitive to energy disturbances, and in hunter-gather societies that sometimes walked long distances, too much energy expenditure could complicate a woman’s ability to conceive. The researchers believe this provides an added layer of information for interpreting fossil footprints of ancient societies.